When i start my 245 up in the morning, after it has been sitting all night, it will start and run fine. But then i might stop the car for a little bit while i go into the store, or whatever, for 10 or 15 minutes. The i start it up again and if this is the second time since i started it up after it had been sitting all night it will give me little accelorator responce. I could slam my foot on the gas and it wouldnt react like it should, like i have no power. so then i let it idle for a few minutes and the car will idle somewhat rough, then it will correct itself and idle fine with much better gas pedal responce. this problem is progressive the more and more i turn it on and off. I took it to a mechanic and he suggested the air mass meter. I foung a used on that worked, and the car seemed like it had a little more power but it still had the problem at start up. Could it be my leaky head gasket, fuel pump, o2 sensor?